Crash fix

src/Dmf_BusFilter.c

@@ -429,14 +429,29 @@ Return Value:
 
     if (stack->MajorFunction == IRP_MJ_PNP)
     {
-        ntStatus = DMF_BusFilter_DispatchPnp(DeviceObject, Irp, stack->MinorFunction);
+        // Capture the minor code BEFORE dispatching. For IRP_MN_REMOVE_DEVICE,
+        // DispatchPnp completes the IRP (invalidating `stack`) and deletes the
+        // device object (invalidating `extension`). Re-reading stack->MinorFunction
+        // afterwards is a use-after-free that can steer us into IoReleaseRemoveLock
+        // on the freed extension.
+        //
+        const UCHAR minorFunction = stack->MinorFunction;
+
+        ntStatus = DMF_BusFilter_DispatchPnp(DeviceObject, Irp, minorFunction);
 
         // For REMOVE_DEVICE, IoReleaseRemoveLockAndWait inside Relations_RemoveDevice
         // has already released the lock (and waited for all other holders). A second
         // release here would corrupt the lock count.
         //
-        if (stack->MinorFunction != IRP_MN_REMOVE_DEVICE)
+        if (minorFunction != IRP_MN_REMOVE_DEVICE)
         {
+            // Safe: this is a non-REMOVE minor, so no teardown path ran, and the
+            // IoAcquireRemoveLock reference taken at function entry is still
+            // outstanding here. That outstanding reference blocks any concurrent
+            // IoReleaseRemoveLockAndWait (in Relations_RemoveDevice / DeviceCleanup)
+            // from completing IoDeleteDevice, so `extension` is guaranteed alive at
+            // the moment we release. We must not touch `extension` after this call.
+            //
             IoReleaseRemoveLock(&extension->RemoveLock, Irp);
         }